Spray painting is a painting technique where a device sprays a liquid coating substance such as paint, ink, or varnish through the air onto a surface. Typically paint is changed into a mist or aerosol, in order to apply a coating onto an object or surface.
Most spray painting is performed with the use of a spray gun. A spray gun combines the coating (paint) and compressed air from a separate air compressor in order to atomize the coating and direct it to the target surface. The coating is held either in a small bottle or container attached to the spray gun or in a separate pressurised container attached to the spray gun with a hose. In a conventional paint-spray gun, the handle of the gun has a tube directly connected with an air compressor to supply pressurized air. The tube is used as a Venturi tube so as to have a paint sprayed on to an object.
It is known that in the production of compressed air, air is drawn from the atmosphere and compressed by a suitable compressor, such as a reciprocating piston, screw type, sliding vane type, centrifugal type, or axially staged blades. The compressed air, however, contains supersaturated water vapour, which condenses upon cooling. If water is not removed from a spray-painting system, there is a tendency for the air passages to become blocked with water. This water can reach the mechanical drive components of the air tools, which prevent their operation and may be very expensive to repair.
Further, in practice it is found that during spraying, the compressor motor gets hot and water vapour in the compressed air condenses into the compressed air tank. Subsequently a stream of compressed air may transport condensed liquid into the paint gun or point of use application. This may result in ‘spitting’ of moisture at the point of application wherein the moisture becomes embedded in the paint work.
Since the moisture and the paint are unable to become a compound, the moisture is usually coated on the surface of an object, and the moisture is covered by the paint sprayed; as a result, the surface sprayed with paint would have moisture spots. The presence of moisture is also known to affect the resultant colour of a paint applied. A blemished pain work cannot be rectified by simply painting over the blemished work.
During the painting process, orange peel, fisheyes, blistering, running, and other imperfections in the coating can be cause for rejection and may result in scrapping the body part. Metal flakes in the paint must be oriented parallel to the body surface to increase reflectivity. The consequences of paint surfaces which do not meet the required minimum standards is very costly. The overall quality of the paint on a vehicle for example can play a major role in selection of a car for purchase.
The overall costs associated with painting are very large. Failure to achieve the required quality and luminosity in the paint surface adds greatly to the overall cost.
The automobile industry needs a solution to the spray problem. A great deal of effort and expense is invested in painting, much of which is wasted. It is absolutely essential, therefore, that as much of the moisture as possible be removed from the compressed air before it is supplied to the devices utilizing this air.
There are several known prior art devices, which seek to avoid the above-enumerated problems. All of these prior art devices accumulate a measured amount of liquid before releasing the accumulated fluid from the compressed air. These devices expel accumulated condensate fluid separated from the compressed air by a float mechanism or by sensitivity to fluid pressure differential which is proportional to the amount of condensate fluid trapped. However, water condensate devices utilizing the aforementioned mechanism are not reliable since the pressure differential mechanisms are subject to clogging and the float mechanisms are subject to seizing. Thus, the aforementioned mechanisms fail to open or, if they open, they fail to close again because of dirt or moisture interfering with the operation of the mechanism.
In another spray painting system currently in use, a filter device consisting of a modified tissue roll is provided within a housing, which device is mounted between a compressor and a spray gun. This type of filter device appears to be an adaptation of an oil filter device described in any one of U.S. Pat. Nos. 2,661,846; 3,317,045; and 3,487,942.
In U.S. Pat. No. 3,317,045 for example, an oil filter device is envisaged utilizing a conventional toilet roll as a filter medium to minimise cost of replacement of an oil filter cartridge, which is both expensive and recommended to be replaced as often as engine oil is changed. In commercial spay painting systems, adaptation of such devices as a means of preventing passage of moisture from a compressor through to the paint reservoir has been attempted and proved to be ineffective, and generally results in total disintergration of the toilet paper roll.
In order to overcome the above problems with the use of a conventional toilet roll, the filter device uses a manufactured filter cartridge to improve resistance to disintergration by a stream of compressed air. The manufactured filter cartridge consists of an impervious plastic core and wound outer roll of compressed paper material. It is found however that the moisture filter function of the manufactured filter cartridge fails after several uses because air/fluid flow results in formation of channels in the filter cartridge hence only the impurities filtering function is workable.
In order to address the adverse effect of channel formation in the manufactured filter cartridge product, it is recommended that the cartridge product be replaced at least once a week at a cost of about $30.00 per cartridge. Such frequent replacement of the cartridge with a refill cartridge represents a very substantial cost relative to the cost of the filter device. Further improvement of filtering devices in the spray painting industry is therefore required to improve efficiency and reduce costs.
Another filter device recently available on the market includes a replaceable dessicant cartridge mounted within a housing. As with the prior art discussed above, the problem with this type of system is that the cartridge is very expensive and requires regular replacement in order to maintain optimum filtering efficiency.
It is to be understood that any discussion of prior art heretofor is not an admission that such art constitutes an acknowledgement of common general knowledge.
It is therefore an object of the present invention to address one or more of the disadvantages of the prior art.
It is a further object to provide a filter system which can provide the public with a useful alternative, which is cost effective and uses conventional toilet paper.